Newer generations of aircraft and other air and space vehicles, including military aircraft, are increasingly using fiber optic connections, rather than metallic wiring, for communications, weaponry, and other systems. Optical fiber connections provide faster communication speed, increased bandwidths, EMI isolation and light weight. However, optical fiber can be more fragile than metallic wiring and can be damaged during installation, during the rigors of flight testing or during flight operation.
Damage to optical fiber can be difficult to distinguish from faults occurring in other components of the aircraft systems. Even when it is known that the damage exists, it can be difficult to identify the precise location of the damage. These difficulties can increase the maintenance costs and reduce the operating efficiency of the aircraft.
One solution to decrease the maintenance costs of any complex system that uses fiber optic connections is to implement built-in test (BIT) capability. BIT capability may be incorporated directly into the fiber optic transceiver module that is otherwise responsible for transmitting and receiving signals via the optical fibers in the cable plant of an airplane. Transceivers with BIT capability may also be employed in local area networks in the telecommunication industry where fibers are buried underground or installed inside tight building space. With BIT capability in a transceiver module, the optical fiber can be routinely tested for any discontinuities in the optical fiber that are indicative of damage. For example, the optical fiber can be tested for breaks and contamination every time the system is started. A transceiver having BIT capabilities identifies the precise location of the fiber damage, thereby avoiding costly maintenance and repairs where the entire fiber network needs to be checked with bulky and expensive equipment operated by expensive, highly skilled personnel.
Hardware installed on certain aircraft (such as military aircraft) must meet certain specification requirements. For instance, small-form-factor (SFF) specifications may be required for certain fiber optic transceiver modules in an aircraft. SFF specifications for a transceiver are design standards resulting from a multi-source agreement (MSA) developed by major commercial fiber optic transceiver suppliers. Certain military and aerospace platforms are installed with SFF transceivers but without BIT capabilities. As a result, such conventional fiber optic systems using SFF transceivers without BIT capabilities require expensive maintenance and repair costs when fiber damage occurs in the cable plant. It is therefore highly desirable to have a fiber optic transceiver module that meets SFF requirements and also has built-in test capability.